After years of experience in PCB design, certain best practices have emerged. Here, we outline essential aspects of PCB layout, wiring, copper plating, and more, with a focus on optimizing performance and manufacturability.
1. Layout and Wiring Impact on Electrical Performance
- Separate Digital and Analog Ground: Although challenging, separating these can reduce noise. Understanding IC electrical characteristics and signal paths helps with efficient layout.
- IC Placement: Components prone to electromagnetic radiation should be near the power source, while sensitive signal processing elements should be close to the signal input for a better signal-to-noise ratio.
2. Copper Plating Considerations
- Signal Routing: For high-frequency signals, narrow, short traces are preferred due to skin effect. Wider copper traces are suitable for low-frequency signals but can degrade high-speed data signals.
- Data Synchronization: Consistent trace widths and lengths are crucial for ensuring synchronization in data channels. Use serpentine traces to adjust signal delays and ensure accurate data transmission.
- Shielding: Large-area copper plating is used for electromagnetic shielding, especially on double-sided boards where the ground plane acts as the shielding layer.
3. Multi-Layer PCB Interlayer Layout
- Four-Layer Board Setup: Power planes should be placed centrally between signal layers. Avoid routing signals between power layers to enhance isolation and minimize interference.
- Shielding: Power layers provide natural shielding in multi-layer designs, improving overall board performance and aiding manufacturing yields.
4. Via Design
- Minimize Vias: Vias introduce capacitance and may generate burrs or electromagnetic radiation. Opt for smaller vias (e.g., 0.5mm or 0.8mm) to reduce the risk of burrs while maintaining production efficiency.
- Burr Prevention: Smaller via apertures have a lower likelihood of producing burrs, improving board quality.
5. Software Application
- Familiarity with Tools: The choice of design software (e.g., PADS, PROTEL) is less important than understanding how to use it efficiently.
- Non-Standard Holes: For non-circular holes, create a custom layer to describe them. Use wireframe shapes that are filled in and well-documented to ensure correct interpretation by the manufacturer.
6. Sending the PCB for Manufacturing
When submitting files to a manufacturer, ensure you provide:
- PCB Computer Files: Include all necessary design files.
- Layering Scheme: Provide details on the layer layout (e.g., circuit map, mechanical structure map).
- Manufacturing Process Requirements: Specify board material (e.g., flame-retardant), surface finishes (e.g., gold plating, copper plating), and thickness.
- Sample Quantity: Clearly indicate the number of boards required.
- Contact Information: Include contact details for follow-up.
By following these guidelines—such as optimizing trace width, minimizing via use, and ensuring proper documentation for manufacturing—you can significantly improve the performance, reliability, and manufacturability of your PCB designs.
